Metering doses of sample liquids

Abstract

A device and method of metering and mixing a dose of a sample liquid with a diluent liquid includes introducing a sample liquid into a channel defined in a housing. The housing defines a pocket open to the channel and sized to both collect a metered dose of the sample liquid, and to retain the collected dose by capillary force when the channel is emptied. The sample liquid is then removed from the channel under conditions that enable retention of the collected, metered dose of the sample liquid in the pocket. Following a cleaning step, a volume of diluent liquid is introduced into the channel to induce diffusion and mixing of the diluent liquid with the dose of sample liquid to form a mixture.

1. A pipette comprising:
 an elongated body having an outer surface and an interior wall, a portion of the interior wall defining an internal cavity; and 
 the body defining a first opening extending through a first end of the body to the internal cavity and a second opening extending through a second end of the body to the internal cavity; 
 wherein the portion of the interior wall defining the internal cavity also defines a pocket open to the internal cavity, the pocket located between the first opening and the second opening; and 
 wherein the pocket is elongated in a direction parallel to a longitudinal axis of the body, such that a ratio of an overall length of the pocket (as measured parallel to the longitudinal axis of the pipette) to an overall width of the pocket is between 10:1 and 25:1. 
 
     
     
       2. The pipette according to  claim 1  wherein the body is formed from a synthetic resin. 
     
     
       3. The pipette according to  claim 1  wherein the pocket is sized and configured to collect a metered dose of sample liquid between about 1 nanoliter and about 10 microliters in volume. 
     
     
       4. The pipette according to  claim 3  wherein the pocket is sized and configured to collect a metered dose of sample liquid between about 5 nanoliters and about 10 microliters in volume. 
     
     
       5. The pipette according to  claim 1  wherein the overall length of the pocket is between about 0.01 and about 1 inch (0.25 and 25 millimeters). 
     
     
       6. The pipette according to  claim 5  wherein the pocket has a width of between about 0.001 and about 0.04 inch (0.025 and 1.02 millimeters). 
     
     
       7. The pipette according to  claim 1  wherein the pocket has a depth of between about 0.001 and about 0.100 inch (0.025 and 2.54 millimeters), measured along a radial line extending from the longitudinal axis of the pipette. 
     
     
       8. A pipette comprising:
 an elongated body having an outer surface and an interior wall, a portion of the interior wall defining an internal cavity; 
 the body defining a first opening extending through a first end of the body to the internal cavity and a second opening extending through a second end of the body to the internal cavity such that air can be drawn from the cavity through the first opening to draw liquids into the cavity through the second opening; 
 wherein the portion of the interior wall defining the internal cavity also defines a pocket open to the internal cavity, the pocket radially extending into the portion of interior wall defining the internal cavity, the pocket sized and configured to collect and releasably retain a metered dose representative of a liquid drawn into the cavity as the cavity is otherwise evacuated through the second opening; and 
 wherein the body defines a plurality of said pockets spaced apart from one another. 
 
     
     
       9. The pipette according to  claim 8 , wherein at least one of the pockets is sized and configured to collect a metered dose of sample liquid between about 1 nanoliter and about 10 microliters in volume. 
     
     
       10. The pipette according to  claim 9 , wherein at least one of the pockets is sized and configured to collect a metered dose of sample liquid between about 5 nanoliters and about 10 microliters in volume. 
     
     
       11. The pipette according to  claim 8 , wherein at least one of the pockets comprises an upwardly extending notch defined in the interior wall of the body. 
     
     
       12. The pipette according to  claim 8  wherein the surface of the pipette defining the lower extent of each of the pockets is substantially perpendicular to a longitudinal axis of the body. 
     
     
       13. The pipette according to  claim 8 , wherein at least one of the pockets is elongated parallel to a longitudinal axis of the body. 
     
     
       14. The pipette according to  claim 13 , wherein at least one of the pockets has a length of between about 0.01 and about 1 inch (0.25 and 25 millimeters), as measured parallel to the longitudinal axis of the pipette. 
     
     
       15. The pipette according to  claim 14 , wherein at least one of the pockets has a width of between about 0.001 and about 0.04 inch (0.025 and 1.02 millimeters). 
     
     
       16. The pipette according to  claim 8 , wherein at least one of the pockets is defined in a protrusion extending into the internal cavity. 
     
     
       17. The pipette according to  claim 8 , wherein the outer surface and the interior wall of the elongated body are substantially parallel such that the radial extension of at least one of the pockets into the interior wall of the elongated body results in a portion of the elongated body which is thinner than adjacent portions of the elongated body. 
     
     
       18. The pipette according to  claim 8 , wherein at least one of the pockets is sized and configured such that capillary forces collect and releasably retain a metered dose representative of a liquid drawn into the cavity as the cavity is otherwise evacuated.